Audio encoders, audio decoders, systems, methods and computer programs using an increased temporal resolution in temporal proximity of onsets or offsets of fricatives or affricates

Abstract

An audio encoder for providing an encoded audio information on the basis of an input audio information has a bandwidth extension information provider configured to provide bandwidth extension information using a variable temporal resolution and a detector configured to detect an onset of a fricative or affricate. The audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that bandwidth extension information is provided with an increased temporal resolution at least for a predetermined period of time before a time at which an onset of a fricative or affricate is detected and for a predetermined period of time following the time at which the onset of the fricative or affricate is detected. Alternatively or in addition, the bandwidth extension information is provided with an increased temporal resolution in response to a detection of an offset of a fricative or affricate. Audio encoders and methods use a corresponding concept.

The invention claimed is: 
     
       1. An audio encoder for providing an encoded audio information on the basis of an input audio information, the audio encoder comprising:
 a bandwidth extension information provider configured to provide bandwidth extension information using a variable temporal resolution; 
 a detector configured to detect an onset of a fricative or an onset of an affricate; 
 wherein the audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that bandwidth extension information is provided with an increased temporal resolution at least for a predetermined period of time before a time at which an onset of a fricative or an onset of an affricate is detected and for a predetermined period of time following the time at which the onset of the fricative or the onset of the affricate is detected; 
 wherein the bandwidth extension information provider is configured to provide the bandwidth extension information such that the bandwidth extension information is associated with temporally regular time intervals of equal temporal lengths, 
 wherein the bandwidth extension information provider is configured to provide a single set of bandwidth extension information for a time interval of a given temporal length if a first temporal resolution is used, and 
 wherein the bandwidth extension information provider is configured to provide a plurality of sets of bandwidth extension information associated with time sub-intervals for a time interval of the given temporal length if a second temporal resolution is used; 
 wherein the audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that at least one time sub-interval, to which a set of bandwidth extension information is associated, immediately precedes another time sub-interval during which an onset of a fricative or an onset of an affricate is detected, 
 such that in at least the one time sub-interval, which precedes the another time sub-interval in which an onset of a fricative or an onset of an affricate is detected, the increased temporal resolution is used; 
 wherein another set of bandwidth extension information is associated to the another time sub-interval. 
 
     
     
       2. The audio encoder according to  claim 1 , wherein the audio encoder is configured to switch from the first temporal resolution for the provision of the bandwidth extension information to the second temporal resolution for the provision of the bandwidth extension information in response to the detection of the onset of a fricative or the onset of an affricate,
 wherein the second temporal resolution is higher than the first temporal resolution. 
 
     
     
       3. The audio encoder according to  claim 1 , wherein the audio encoder is configured to sub-divide a given time interval of the given temporal length into four sub-intervals of equal lengths, if an increased temporal resolution is used to provide the bandwidth extension information for the given time interval of the given temporal length,
 such that four sets of bandwidth extension information are provided for the given time interval of the given temporal length. 
 
     
     
       4. The audio encoder according to  claim 1 ,
 wherein the audio encoder is configured to selectively use an increased temporal resolution to provide bandwidth extension information for a first time interval of a given temporal length preceding a second time interval of the given temporal length, 
 if an onset of a fricative or an onset of an affricate is detected within the second time interval and if a temporal distance between a time at which the onset of the fricative or the onset of the affricate is detected and a border between the first time interval and the second time interval is smaller than a predetermined temporal distance. 
 
     
     
       5. The audio encoder according to  claim 1 ,
 wherein the audio encoder is configured to perform a temporal look-ahead, such that an increased temporal resolution is used to provide bandwidth extension information for a first time interval of a given temporal length preceding a second time interval of the given temporal length in response to a detection of an onset of a fricative or of an onset of an affricate in the second time interval. 
 
     
     
       6. The audio encoder according to  claim 1 ,
 wherein the audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that bandwidth extension information is provided with a same increased temporal resolution at least for a predetermined period of time before a time at which an onset of a fricative or an onset of an affricate is detected and for a predetermined period of time following the time at which the onset of the fricative or the onset of the affricate is detected. 
 
     
     
       7. The audio encoder according to  claim 1 ,
 wherein the audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that sets of bandwidth extension information are provided with same increased temporal resolutions at least for a first time sub-interval, a second time sub-interval and a third time sub-interval, 
 wherein the first time sub-interval immediately precedes the second time sub-interval; 
 wherein an onset of a fricative or an onset of an affricate is detected in the second time sub-interval; and 
 wherein the third time sub-interval immediately follows the second time sub-interval. 
 
     
     
       8. The audio encoder according to  claim 1 ,
 wherein the detector is configured to detect an offset of a fricative or affricate; and 
 wherein the audio encoder is configured to adjust a temporal resolution used by the bandwidth extension information provider such that bandwidth extension information is provided with an increased temporal resolution at least for a predetermined period of time before a time at which an offset of a fricative or affricate is detected and for a predetermined period of time following the time at which the offset of the fricative or affricate is detected. 
 
     
     
       9. The audio encoder according to  claim 1 , wherein the detector is configured to evaluate a zero crossing rate, and/or an energy ratio, and/or a spectral tilt in order to detect an onset of a fricative or an onset of an affricate. 
     
     
       10. The audio encoder according to  claim 1 , wherein the detector is configured to evaluate a zero crossing rate, and/or an energy ratio, and/or a spectral tilt in order to detect an offset of a fricative or affricate. 
     
     
       11. The audio encoder according to  claim 1 , wherein the audio encoder is configured to selectively adjust a temporal resolution used by the bandwidth extension information provider such that bandwidth extension information is provided with an increased temporal resolution in response to a detection of an onset of a fricative or an onset of an affricate only for a speech signal portion but not for a music signal portion. 
     
     
       12. The audio encoder according to  claim 1 , wherein the audio encoder is configured to selectively use an increased temporal resolution to provide bandwidth extension information for a plurality of subsequent time intervals that encompass a time at which an onset of a fricative or an onset of an affricate is detected in response to a detection of an onset of a fricative or of an onset of an affricate or in response to a detection of an offset of a fricative or affricate. 
     
     
       13. The audio encoder according to  claim 12 , wherein the audio encoder is configured to selectively use an increased temporal resolution to provide bandwidth extension information for a plurality of subsequent time intervals that fully encompass an onset of a detected fricative or affricate. 
     
     
       14. A system, comprising:
 an audio encoder according to  claim 1 ; and 
 an audio decoder configured to receive the encoded audio information provided by the audio encoder, and to provide, on the basis thereof, a decoded audio information, 
 wherein the audio decoder is configured to perform a bandwidth extension on the basis of the bandwidth extension information provided by the audio encoder, 
 such that the bandwidth extension is performed with an increased temporal resolution at least for a predetermined period of time before a time at which an onset of a fricative or an onset of an affricate is detected and for a predetermined period of time following the time at which the onset of the fricative or the onset of the affricate is detected, or 
 such that the bandwidth extension is performed with an increased temporal resolution at least for a predetermined period of time before a time at which an offset of a fricative or affricate is detected and for a predetermined period of time following the time at which the offset of the fricative or affricate is detected. 
 
     
     
       15. A method for providing an encoded audio information on the basis of an input audio information, the method comprising:
 providing bandwidth extension information using a variable temporal resolution; and 
 detecting an onset of a fricative or an onset of an affricate; 
 wherein a temporal resolution used for providing the bandwidth extension information is adjusted such that bandwidth extension information is provided with an increased temporal resolution at least for a predetermined period of time before a time at which an onset of a fricative or an onset of an affricate is detected and for a predetermined period of time following the time at which the onset of the fricative or the onset of the affricate is detected; 
 wherein the bandwidth extension information is provided such that the bandwidth extension information is associated with temporally regular time intervals of equal temporal lengths, 
 wherein a single set of bandwidth extension information is provided for a time interval of a given temporal length if a first temporal resolution is used, and 
 wherein a plurality of sets of bandwidth extension information associated with time sub-intervals is provided for a time interval of the given temporal length if a second temporal resolution is used; 
 wherein a temporal resolution used is adjusted such that at least one time sub-interval, to which a set of bandwidth extension information is associated, immediately precedes another time sub-interval during which an onset of a fricative or an onset of an affricate is detected, 
 such that in at least the one time sub-interval, which precedes the another time sub-interval in which an onset of a fricative or an onset of an affricate is detected, the increased temporal resolution is used, 
 wherein another set of bandwidth extension information is associated to the another time sub-interval. 
 
     
     
       16. A non-transitory digital storage medium having stored thereon a computer program for performing a method according to  claim 15  when the computer program runs on a computer.